1. Field
This disclosure relates generally to battery charging, and more specifically, to battery chargers that equalize charge on the battery cells.
2. Related Art
Battery charging systems are often used for batteries that have a number of cells that are connected in series. As charging occurs, each cell is charged from current that is supplied by a charger. Due to a variety of factors that may come into play during manufacturing and use, it may turn out that the cells are not all charged at the same rate to the desired level, especially as the battery ages. In such case some cells are charged to a greater level than others which has the potentially harmful effect of overcharging some cells. There is then the issue of the degree of overcharging that may be harmful versus the problem of one or more cells not reaching the desired level. Thus, there is a continuing preference to avoid overcharging any cells while still obtaining the desired level of charge for any of the cells.
Accordingly, there is a need for improved charging that reduces problems with overcharging while efficiently obtaining the desired level of charge of all of the cells such as transferring energy efficiently from cell to another cell in the battery pack using a DC to DC converter.